advent-of-code-2021/day-01/day-01-01.sml

(* open IntInf; *)

fun read file =
    let
        val inStream = TextIO.openIn file
    in
        (* TextIO.inputAll returns a TextIO.vector, which is a string. *)
        TextIO.inputAll inStream
    end;

fun count_increases [] = 0
  | count_increases [n] = 0
  | count_increases measurements =
    let
        val (first_measurement::rest_measurements) = measurements;

        fun iter (remaining, previous, accumulated) =
            if List.null remaining
            then
                accumulated
            else
                let
                    val (current::rest) = remaining;
                in
                    if current > previous
                    then
                        let
                            val _ = print ((Int.toString current) ^ " > " ^ (Int.toString previous) ^ "\n");
                        in
                            iter (rest, current, accumulated + 1)
                        end
                    else
                        iter (rest, current, accumulated)
                end
    in
        iter (rest_measurements, first_measurement, 0)
    end;



val str = read "input";
val lines = String.tokens (fn c => c = #"\n") str;
val measurements = map (fn num_as_str =>
                           case Int.fromString num_as_str of
                               SOME number => number
                             | NONE =>
                               raise Fail "encountered a non-int string")
                       lines;

count_increases measurements;